Tag Archives: semiconductor

Room-Temperature NDR Polymer Diodes for Flexible, Low-Power Electronics

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Summary:

Devices that exhibit a phenomenon known as negative differential resistance (NDR) have tremendous potential to deliver the kind of low-power circuitry needed in a variety of electronics applications. To understand NDR, it is instructive to recall Ohm’s Law, V=IR. For a fixed resistance (R), as voltage (V) increases, current (I) increases in a linear fashion. In NDR, there is a voltage range where increasing voltage actually results in a decreasing current. This behavior has many beneficial design properties, one of which is the design of low power memory and logic or even energy scavenging from the environment, eliminating the need for a self-contained battery.

Until now, successful demonstrations of NDR have been limited to rigid, inflexible semiconductor-based devices that are unsuitable for certain applications. Researchers at The Ohio State University have developed a polymer-based device that exhibits NDR and has the flexibility needed for advanced applications such as smartcards and wearable electronics. These devices enjoy very fast operation, which leads to high performance while consuming very little power. Furthermore, these devices can be manufactured in a very cost-effective manner using simple printing techniques.

Potential Applications:

  • Smartcards
  • Energy Scavenging
  • Development of advanced logic and memory circuits on flexible substrates

Advantages:

  • Large and reproducible NDR, at room temperature, in a flexible polymer device!
  • Low cost and simple solution processing
  • Fast operation at low power

Direct, Low Frequency Capacitance Measurement for Scanning Capacitance Microscopy

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Summary:

Scanning capacitance microscopy (SCM) circuits, used for such applications as semiconductor characterization (including dopant profiling, device characterization, and surface defect characterization), are typically not adapted for calibrated, low frequency measurements of absolute capacitance. In fact, these implementations of SCM generally do not measure capacitance directly. Rather, they measure the change in capacitance versus the change in voltage (dC/dV) by varying the probe-sample voltage V at frequencies greater than 10 kHz. This is due to a voltage dependant capacitance resulting from a voltage-dependant space change layer in the semiconductor substrate. The Ohio State University has developed a system and method for performing scanning capacitance microscopy using an atomic force microscope (AFM) that measures direct capacitance at a frequency less then 10 kHz. The system exhibits high sensitivity with very low noise. Recent advancements to this technology have resulted in even higher sensitivity by enabling direct measurements of absolute capacitance at higher frequencies. The design of the circuit has also been simplified, enabling the use of off-the-shelf components such as function generators. This straightforward design will shorten the investment of time and money needed to commercialize this powerful system.

Potential Applications:

This system is an ideal tool for semiconductor characterization. It is also useful for measuring a wide variety of dielectric films such as SiO2 grown on Si, or for dielectric films on other semiconductor substrates such as Si3N4, Al2O3, TiO2, and ZrO2. It may also be used to measure thin lubricant films such as perfluoropolyethers, a widely used class of compounds for MEMS and hard disk drive lubrication. Other suitable types of samples include self-assembled monolayers.

Advantages:

  • Enables direct capacitance measurements at low frequencies
  • Low noise
  • High sensitivity
  • Straightforward yet powerful design
  • Can also determine stray capacitance

Advanced High-Efficiency Nanowire LEDs

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Summary:

There is great interest in developing new solid state semiconductor-based light emitting diodes (LEDs) that exhibit new functionality and performance. Principal challenges in creating new semiconductor LED structures include the formation of defects and low doping efficiency, both of which negatively affect device performance. To overcome these challenges, researchers at The Ohio State University have developed new methods and device structures that lead to defect-free, high-efficiency nanowire LEDs. These LEDs can be easily mass manufactured and integrated in silicon electronics, and can hit any bandgap due to the lack of strain relaxation.

Potential Applications:

  • Lighting
  • Laser diodes
  • Photodetectors
  • Communications
  • Sensors

Advantages:

  • Defect-free formation during epitaxial growth
  • Extremely high-efficiency
  • Low resistance
  • Enables simple and broad bandgap engineering
  • Low manufacturing costs and easy integration into Si electronics

Low Temperature Working Carbon Monoxide (CO) Sensor Based on Au/SnO2 Core-Shell Nanoparticles

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Summary:

SnO2-based CO sensors are widely used in domestic and industrial applications and belong to the class of metal-oxide semiconductor (MOS) sensors. This class of sensor is easy to manufacture and miniaturize, and sensitivity and selectivity are both tunable. Also, electrochemical measurements are easily realized, require simple electronics, and integration into electronic devices is straightforward. However, since sufficient oxygen vacancies are needed for conduction, MOS sensors typically operate at elevated temperatures, which requires energy consumption and reduces sensor lifetimes. Researchers at The Ohio State University have developed a MOS CO sensor based on Au/SnO2 core-shell nanoparticles that is operable in the 25 to 150 deg. C range. Sensor response is highly reproducible and recovery is fast in this temperature range, and high sensitivity was exhibited.

Potential Applications:

  • Home, office, and industrial CO monitoring for occupant and fire safety
  • Low temperature and low power requirement makes it compatible with mobile devices

Advantages:

  • A MOS electrochemical CO sensor that operates in the 25 to 150 deg. C range!
  • Increased safety and sensor longevity as no heating device is needed
  • Greatly reduced energy consumption
  • Extremely low cost and easy manufacturing
  • Simple electronics for easy device integration

Cantilever Couplers for Intra-Chip Coupling to Silicon Photonic Integrated Circuits

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Summary:

As electronics continue to get smaller and faster, standard copper connections between devices will prove to be inadequate for transmitting such high-bandwidth data. A more efficient and high-bandwidth solution is to use photonics, where data is transmitted via light in fiber-optic cables rather than via electrons on a copper wire. Photonic components are expensive, however, and in order to reach mass manufacturing status photonics must somehow be integrated into circuits based on silicon. This is difficult as coupling light directly to silicon integrated circuits has required dicing or cleaving the circuit in some way. Researchers at The Ohio State University have invented a way to efficiently couple light from an optical fiber to silicon photonic integrated circuits at any location on the surface of the circuit without the need to dice or cleave the circuit. This is achieved using on-chip cantilever couplers that can be fabricated using standard CMOS processes used in the semiconductor integrated circuit industry. This technique is an important step towards the widespread realization of optoelectronic devices based on silicon.

Potential Applications:

  • Optical interconnects
  • Low-cost telecommunications
  • Optical Sensors
  • Could revolutionize computing by allowing nearly limitless bandwidth

Advantages:

  • Couples light to silicon photonic ICs without the need to dice or cleave the circuit
  • Efficient and low-loss coupling method
  • Can couple light at any location on the surface of the circuit
  • Cost effective and mass producible as the invention is silicon-based

Emulating Metamaterials Using a Simple Printed Microstrip Design

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Summary:

Researchers at the Ohio State University’s ElectroScience Laboratory have been able to use simple (printed on uniform substrates) microwave circuit components to emulate the extraordinary propagation phenomena traditionally encountered in photonic crystals and metamaterials. These materials have been shown to exhibit unique and useful properties for microwave and optics applications such as delay lines, couplers, and antennas. One class of these structures demonstrated significant wave slowdown and amplitude increase within a small region, leading to miniaturization of antennas and other microwave circuit components. Another important property of metamaterials that has attracted significant research interest is the realization of a negative index of refraction. As the latter are difficult and expensive to manufacture, the proposed technology provides a practical approach to realize such unique properties. The researchers have already been able to realize these extraordinary properties using uniquely invented, cost effective, and easy to manufacture microstrip transmission lines arrangements.

Potential Applications:

  • Enables easy and inexpensive miniaturization of microwave and optical circuit components such as coupled lines, delay elements, phase shifters, printed antennas, antenna arrays, and solid state semiconductor optoelectronic devices
  • Enjoys the benefits derived from photonic crystals and metamaterials at a fraction of the cost
  • Enables a boost in gain while maintaining the same size dimensions

Advantages:

  • Compared to photonic crystals and metamaterials, this structure is much more cost effective and easier to manufacture, while exhibiting similar properties
  • Easy to retrofit with existing manufacturing processes and manufacture in volume since it is based on printed circuit technology